Marciano Brunette Never Cheated on Jessi Draper, Despite Viral 'VPR' Episode

Marciano Brunette did not cheat on Jessi Draper, despite a viral scene from "Vanderpump Rules: Lisa Las Vegas" that had fans accusing him of stepping out on his reality star girlfriend … TMZ has learned.

The drama erupted after a scene from the new Vanderpump show went viral online, with the timing make it look like Marciano made out with another woman while he was dating Jessi.

Sources with direct knowledge tell TMZ ... the encounter happened back in May, when Marciano and Jessi had only been casually dating for about a month. We're told the pair didn't become exclusive until August.

One source tells us straight up ... Marciano "has never cheated on Jessi and never will."

The controversy comes after the pair's relationship already made headlines on "The Secret Lives of Mormon Wives," where their connection became a major storyline amid Jessi's marital troubles and eventual divorce from Jordan Ngatikaura.

Now, the latest Bravo footage has reignited questions about whether Marciano was faithful ... but sources insist he didn't break any exclusivity because the couple wasn't even there yet.